distill 1.6

• RSS feed creation now works correctly for listings when no description is provided in one of the Rmd post (thanks, @cpsyctc, @apeterson91, #490, #448).
• Fix an issue with line numbering on code chunks when highlight-downlit: false by tweaking Pandoc's default CSS rules (thanks, @SES-CE, #473).
• Internally use format() instead of as.character() with Dates to account for argument format= deprecation in R 4.3.0 (thanks, @mbojan, #488).
• Add a subtitle variable in HTML template placed between title and categories (thanks, @dicook, #480).
• Add author name in orcid image alt text (thanks, @mitchelloharawild , @ajrgodfrey, #494, rjournal/rjtools#86).
• In distill_article(), metadata header in HTML is separated by <hr> to improve accessibility (thanks, @mitchelloharawild, #495, @ajrgodfrey, #rjournal/rjtools#92)